Chassis of electronic devices, such as laptop personal computers (laptop PCs), tablet personal computers (tablet Ps), smartphones, and cellular phones, need to be lightweight, thin and strong. In view of this, a fiber-reinforced resin, e.g., carbon fiber reinforced plastics (CFRP), in which reinforced fibers, e.g., carbon fibers, are impregnated with a resin has been widely employed for chassis of electronic devices.
For example, as shown in FIG. 10, in order to form a through hole 31 for screws or a through hole 31A as air inlet/outlet in a fiber-reinforced resin material 101, a technique known to-date includes a primary process of shaping a fiber-reinforced resin material 101 is performed, and then a secondary process of press-cutting with a press cutter, machining with a milling cutter, or cutting with a laser is performed. However, with the above-mentioned processing technique, the entire part of reinforced fibers 10 corresponding to through hole 31 or 31A is cut off and removed in a hole forming step as illustrated in FIGS. 11-12, resulting in the problem of a decrease in strength of a region around the through hole 31 or 31A.
Since the fiber-reinforced resin material is strong, press-cutting or machining can shorten the life of a tool, resulting in another problem of increased costs. In addition, since the fiber-reinforced resin material needs to be irradiated with high-power laser light for a long period in laser processing, the matrix resin around the through hole is burnt, resulting in yet another problem of a failure in forming a normal through hole.
Consequently, it would be preferable to provide an improved method for processing a fiber-reinforced resin material without a decrease in strength after processing, without an increase in costs, and without a degradation of processing accuracy.